Brochure Heraeus Original Hanau D 310625/2C 9.89/VN PK, published in 1989 by W. C. Heraeus GmbH, parent company of the assignee of the present application, discloses, on page 13 thereof, an immersible lamp of modular construction and featuring a high-pressure mercury discharge tube 1. FIG. 8 shows that the discharge tube is fastened with a discharge tube holder 2 and electrical supply line, using clamps and seals. The immersible tube 4, in turn, is suspended within a cooling tube 5 with clamps and seals. A head plate 3.3 supports the tubes and is equipped with an inlet 3.1 and an outlet 3.2 to permit a flow of inert gas to cool the tubes. The cooling tube offers the possibility of water cooling between immersible tube and reaction mass. The connection of the head plate or immersible lamp head with the immersible tube, as well as the connection of the immersible tube with the cooling tube, is accomplished by means of standard flange connections.